Achieving a high yield of good integrated circuits is generally of critical importance to integrated circuit manufacturers. Accordingly, manufacturers often attempt to identify and address the cause of defects, when defects are detected. Tracking the batches or the particular wafers corresponding to defective chips can sometimes help identify the cause of defects. Accordingly, wafers are often marked with a unique ID or serial number that permits a manufacturer to keep a database containing the processing histories of the wafers.
Cutting a wafer separates the identifying marks from the resulting chips, so that tracking the source of a particular chip becomes very difficult after cutting. In particular, tracking individual chips can be done by marking the individual chips, which can be a time consuming additional processing step, and then maintaining a database indexed by the identifying marks on the chips. Chips might also be identified according to their position on processing equipment, but such identification is error prone.
Testing of the integrated circuits is also critical to quality control and to achieving a high yield of good IC chips. Accordingly, IC chips are generally subject to a series of quality control tests before and after packaging. Comparing the results of the separate tests can prove useful, but tracking and correlating the results of these tests presents the difficulty of identifying individual chips and then matching the chips with prior test results.
In view of the limitations of current techniques for identifying individual chips and matching data with specific chips, better structures and processes are sought for tracking of information associated with the manufacture of integrated circuits.